High sensitivity magnetic actuator

Abstract

An improved magnetic actuator for providing mechanical actuation representative of an input current has a housing that supports a coil surrounding a central core, and includes a diaphragm type spring above the central core. A cover of high magnetic permeability is mounted on the housing spaced from the diaphragm spring. A permanent magnet is mounted on the diaphragm spring in a predetermined pole orientation and the magnet extends through an opening in the cover. The permanent magnet provides flux through the housing and the core. Sensitivity is increased by using the permanent magnet to provide a magnetic flux in addition to that created by currents in the coil. The magnet is oriented in relation to current flow in the coil so that the flux from the magnet will add to that generated by the coil in the gap between the pole face formed by the core and the spring and will subtract from the flux generated by the coil in the gap between the spring and the cover to provide a substantially linear deflection versus current relationship. The diaphragm spring is a sandwich of a pair of spider like spring discs having a thin layer of rubber between the plates to provide dampening to reduce sensitivity to vibration while aiding in providing linear operation.